Subject: Project Number P1576 (Proposed Standard for Lightning
Protection System Using the "Charge Transfer System" for Industrial
and Commercial Installations.)
Dear Administrator Haasz:
The purpose of this communication is to recommend that
the IEEE be extraordinarily careful in its consideration of the proposed
standard. Before a standard for the use of "Charge Transfer Systems"
is issued, the Standards Board members should obtain and assess information
on the electrical responses by these devices under active thunderstorms
that has been measured by competent, independent investigators.
The present consensus held by members of the lightning
and thunderstorm electricity community in both the American Geophysical
Union and in the American Meteorological Society about these devices
is that they are replays of Benjamin Franklin's original, failed ideas
about lightning rods. In the course of some parlor experiments, he and
his associates discovered that they could discharge electrified objects
silently, without sparks, by approaching them while holding a sharp-tipped
needle directed at the object. This discovery of the "point discharge"
or "corona current" phenomenon led Franklin to suggest that, perhaps,
thunderclouds could similarly be discharged, thus preventing lightning,
by taking away its electricity. However, after Franklin erected a sharp-tipped
iron rod for this purpose, instead of discharging a thundercloud passing
above, his rod was struck by lightning. Thereafter, Franklin recognized
that a primary function for an elevated rod was to be a lightning receptor
and to carry the lightning to Earth, around structures that were to
be protected.
Despite this new and unexpected function that his rods
appeared to serve, Franklin (1767) remained enamored of the "power of
a point" and recommended that the tips of lightning rods be sharp, a
configuration that is still widely used today although the virtue of
having sharp tips on lightning rods has never been established. Our
assessment of the experience gained since Franklin's time is that sharp
rods and "dissipation arrays" exposed in isolation on high towers are
often struck by lightning but there is no credible evidence that they
prevent lightning, which usually initiates high up in thunderclouds
My associates, Drs. William Rison and Paul Krehbiel in
the Electrical Engineering Department at New Mexico Tech, have constructed
and deployed a "lightning mapping array" that records the occurrence,
with a GPS time tag, of the strongest VHF radiation caused by lightning
every 100 microseconds at each of the ten measuring stations in the
array. By using time-of-arrival techniques, they are the able to locate,
three dimensionally, the location of each source. (For more information
on this array, go to www.lightning.nmt.edu).
Drs. Rison and Krehbiel find that the negative cloud-to-ground
lightning here in New Mexico, in western Kansas and over central Oklahoma
typically starts at altitudes between 5 km (about 16,400 feet) and 6
km (about 20,000 feet) above sea level at heights where it is unaffected
by objects at the surface of the Earth. It is now well established that
surface conditions have little to do with the initiation of cloud-to-ground
lightning discharges, high in thunderclouds.
During the 1969 summer, we were hosts to Willard Starr,
Roy Carpenter's predecessor and father-in-law, during the early field
tests of his "charge-dissipation" system. (Starr believed that the corona
discharges from elevated barbed wires could eliminate lightning, hurricanes
and tornadoes.) We showed Starr how to measure the currents flowing
to his array of barbed-wires, furnished him with a recorder and with
a physical interpretation (which he ignored) of the sudden, large displacement-current
surges caused by the lightning that continued despite his large array
of elevated barbed wires.
In the years since there has been many incidents in which
lightning has struck these "dissipation arrays". There are photographs
of strikes to a tall tower at Eglin Air Force Base, to a 500 foot meteorological
tower at Kennedy Space Center and to a "lightning eliminator" at Langmuir
Laboratory here in New Mexico. Beginning in 1988, the Federal Aviation
Administration carried out a test of "multipoint discharge lightning
protection systems" in Florida. On its termination in 1990, the FAA
Associate Administrator for Airway Facilities, Arnold Aquilano, wrote
to Congressman M. A. Sabo:
Our assessment of the "Dissipation Array System" system
and the concept on which it was based are simply replays of Benjamin
Franklin's failed intent for lightning rods which was to prevent the
occurrence of lightning by neutralizing the charge in thunderclouds
overhead with the emissions from pointed electrodes on the Earth. However,
the charges emitted by a sharp-tipped "charge transfer" device can influence
the last stages of a lightning strike in its vicinity. These charges
can shield the device and thus reduce the chances that it will take
the strike while some other object nearby is hit but this effect is
unpredictable and depends on the wind and on the local geometry.
The undeniable facts are that "dissipation" devices do
not prevent the occurrence of cloud-to- ground lightning strikes and
that they are not designed nor intended to be the preferential receptors
of the lightning strikes in their vicinity. Accordingly, such devices
serve no useful protective purpose in the prevention nor in the reception
and conveyance of lightning to Earth.
In my opinion, the "Charge Transfer System" method does
not have technical merit for lightning protection and there is little
probability that it will acquire any technical merit in the future.
It would be a disservice to the public for the IEEE to
issue a standard supporting the use of these devices as being suitable
for protection against lightning.
Sincerely,
/s/ CBM
Charles B. Moore
Professor Emeritus
Atmospheric Physics
New Mexico Institute of Mining and Technology
